| 著者名 | Authors | 所属機関名 | 所属機関名(欧文) | |
| 1 | #後藤/忠徳 | Goto/Tadanori | 愛知教育大学 | Aichi University of Education |
| 2 | 清水/久芳 | Shimizu/Hisayoshi | 東京大学地震研究所 | Earthquake Research Institute, University of Tokyo |
| 3 | 歌田/久司 | Utada/Hisashi | 東京大学地震研究所 | Earthquake Research Institute, University of Tokyo |
| 4 | 田中/良和 | Tanaka/Tanaka | 京都大学理学部 | Kyoto University |
| 5 | 湯元/湯元 | Yumoto/Kiyofumi | 九州大学理学部 | Kyushu University |
講演予稿:
ナホトカ（ロシア）から直江津（日本）の間を結ぶ日本海ケーブ
ル(JASC)による電位差データを用いてMT解析をおこなった。MT解析
の際には、柿岡の地磁気観測点の地磁気データを使用した。JASCに
よって得られた見かけ比抵抗値と位相差から日本列島下の比抵抗構
造に関してどの程度の制約が与えられるのかを調べるために、日本
列島周辺の3次元的な電気伝導度構造のforward計算を行った。JASC
から得られるMT responseは、深さ100〜400kmのマントルの比抵抗値
を制約できることが分かった。一方、高比抵抗なsubducting slabに
対するJASCの感度については、ほとんどないことが分かった。
abstract:
Electrical potential difference between Nakhodka (Russia) and
Naoetsu (Japan) has been observed by using the Japan Sea Cable
(JASC) since 1996. MT responses were obtained from the observed
data to constrain the conductivity structure beneath the Japan
sea and the West Pacific region for frequency range from 300 sec
to 30,000 sec. Magnetic data from several observatories were
used for testing the inhomogeneity of the source field. Then,
three-dimensional forward modeling, using a code by Mackie et al.
(1993), was carried out to examine how the structure is
constrained by the observed JASC MT response. Following
implications were obtained
(1) The high conductance of the upper
mantle (the depth range of 100 - 400km) beneath the Japan sea is
well constrained by the JASC MT response. It is estimated as
about 15,000 - 25,000 S from the response curve at the periods
longer than 6,000 sec. (2) The lithosphere conductivity is also
sensitive to the MT response by the JASC, but it cannot be
constrained by using JASC only. On-land MT responses are needed
in the modeling process to estimate the lithosphere conductivity
beneath the Japan Sea.
キーワード:
日本海, MT法, 電気伝導度
Keywords:
Japan Sea, magnetotellurics, electrical conductivity